Thermal decomposition behavior of retired wind turbine blades: kinetics, pyrolysis product distribution and characterization

The rapid growth of the wind power industry has heightened the need for effective resource utilization of retired wind turbine blades (RWTB). Pyrolysis technology offers a promising approach for recovering high-value products from RWTB. In this study, the pyrolysis kinetic behavior of RWTB was investigated using three kinetic models (KAS, FWO, Miura) and the isoconversional method, based on thermogravimetric (TG) analysis at four heating rates. The results indicate that the pyrolysis process occurs in four stages, with the active thermal decomposition stage between 300 and 480 °C. The temperature corresponding to the maximum weight loss rate was 380 °C, and the activation energy ranged from 177 to 280 kJ/mol. Rapid pyrolysis experiments were conducted on RWTB in a fixed bed reactor at temperatures of 300-600 °C, the distribution of pyrolysis products (gas, tar, and char) was systematically analyzed. Pyrolytic tar was examined using GC-MS, while pyrolytic char was characterized using SEM, XRD, and Raman spectroscopy. The results indicate that the most complete decomposition of RWTB occurred at 500 °C, with pyrolytic gas and tar yields reaching 3.5 % and 33.6 %, respectively. The gas primarily consisted of CO₂ and CH₄, while the tar was rich in phenolic compounds (up to 76 %), including bisphenol A, phenol, 4-isopropylphenol, and 4-isopropenylphenol. Analysis of the solid residues show that carbon remained on the fiber material surface, with no significant changes in its shape or structure. This study demonstrates the potential of pyrolysis as a sustainable solution for converting RWTB into high-value chemicals while recovering reusable fiber materials.